TCJA Sunset Capital Gains & NIIT Tax Simulator 2027
Project long-term and short-term capital gains taxes, Section 1411 NIIT surtax thresholds, and state additions following the 2025 TCJA sunset.
What Are Your Capital Gains Parameters?
What Is Your Projected Capital Gains Tax Liability?
What Is The Post-TCJA Net Investment Income Surtax Matrix?
Objective: Modeling capital gains liability, Section 1411 NIIT surtaxes, and state additions after 2025 TCJA sunset provisions expire.
- Step 1: Quantify Ordinary Income Baseline: Calculate taxable salary and business income to establish which tier preferential capital gains stack into under IRC Section 1(h).
- Step 2: Measure NIIT Exposure: Test whether aggregate Modified Adjusted Gross Income exceeds unindexed statutory thresholds ($200,000 Single / $250,000 MFJ) to apply Section 1411 surtaxes.
- Step 3: Execute Bracket-Optimized Dispositions: Time realization across calendar tax years or utilize installment sales to prevent involuntary migration into the 20% federal capital gains bracket.
How Do IRC Section 1(h) and Section 1411 Statutory Benchmarks Compare?
Statutory threshold comparison and code references governing capital asset dispositions pre- and post-sunset.
| Tax Tier / Metric | 2026 TCJA Baseline | Projected 2027 Post-Sunset | Statutory Code Authority |
|---|---|---|---|
| 0% Preferential LTCG Tier | Up to $48,350 Single / $96,700 MFJ | Up to $48,350 Single / $96,700 MFJ | 26 U.S. Code Section 1(h)(1)(B) |
| 15% Standard Preferential LTCG | $48,350 to $533,400 Single | $48,350 to $533,400 Single | 26 U.S. Code Section 1(h)(1)(C) |
| 20% Top Federal LTCG Rate | Above $533,400 Single / $600,050 MFJ | Above $533,400 Single / $600,050 MFJ | 26 U.S. Code Section 1(h)(1)(D) |
| 3.8% Net Investment Income Tax (NIIT) | MAGI > $200k Single / $250k MFJ | MAGI > $200k Single / $250k MFJ | 26 U.S. Code Section 1411(b) |
| Maximum Federal Combined Rate | 23.8% LTCG / 40.8% STCG | 23.8% LTCG / 43.4% STCG | IRC Section 1 plus Section 1411 |
| California Top Rate on Capital Gains | 13.3% (Taxed as Ordinary Income) | 13.3% (Taxed as Ordinary Income) | Cal. Rev. and Tax Code Section 17041 |
| New York Combined Top Rate (State + NYC) | 14.776% Combined Top Tier | 14.776% Combined Top Tier | NY Tax Law Section 601 |
How Should You Optimize Capital Gains Strategy for the Post-TCJA Era?
While the Tax Cuts and Jobs Act of 2017 centered its individual tax reforms on ordinary income brackets and standard deductions, its impending statutory sunset on December 31, 2025 directly impacts capital gains tax planning through income stacking interactions. Under Internal Revenue Code Section 1(h), long-term capital gains are layered on top of ordinary income, meaning any increase in ordinary tax liability or bracket compression shifts capital gains into higher marginal territory earlier.
Furthermore, high-earning investors must contend with the Section 1411 Net Investment Income Tax (NIIT). Enacted under the Affordable Care Act, the NIIT imposes an unindexed 3.8% surtax on net investment income for single filers with modified adjusted gross income exceeding $200,000 ($250,000 for married joint filers). Because these thresholds were intentionally excluded from annual inflation adjustments, fiscal drag causes an increasing percentage of mid-career professionals and startup equity holders to trigger the surtax each year.
To mitigate exposure prior to the sunset, taxpayers should evaluate multi-year tax loss harvesting, installment sales under IRC Section 453, and charitable remainder unitrusts (CRUTs) to defer or smooth capital asset dispositions across calendar years.
What Are the Frequently Asked Questions Regarding Capital Gains Taxes?
How does the TCJA sunset affect capital gains tax brackets in 2027?
Under IRC Section 1(h), statutory long-term capital gains rates remain at 0%, 15%, and 20%. However, because the underlying ordinary income brackets expand following the expiration of P.L. 115-97, and standard deductions decrease, many investors find that their capital gains stack into higher marginal brackets earlier.
What is the Net Investment Income Tax (NIIT) and does it expire with TCJA?
The Net Investment Income Tax (NIIT) is a 3.8% surtax established under IRC Section 1411 as part of the Affordable Care Act. It was not part of the TCJA and does NOT expire. It continues to apply to the lesser of net investment income or excess MAGI over $200,000 for single filers and $250,000 for married couples filing jointly.
What is the maximum effective tax rate on capital gains in 2027?
The top federal long-term capital gains rate is 20% plus the 3.8% NIIT surtax, creating a maximum federal rate of 23.8%. When state income taxes are factored in (such as California at 13.3% or New York at 10.9%), high-earning investors face total combined tax rates exceeding 37% on realized gains.